window.onload = function () {
  let power = document.getElementsByTagName("span")[0];
  let timeEach = window.setInterval(function () {
    let powerNum = parseInt(power.innerText);
    power.innerText = parseInt(power.innerText) + 1 + "%";
    if (powerNum >= 99) {
      window.clearInterval(timeEach);
      return;
    }
  }, 1000);
}